Dynamic balance correction station for a disc drive

ABSTRACT

Apparatus for balancing a rotary object, such as a disc drive disc pack. A balance correction member is provided as a C-shaped ring formed from a length of wire of nominally uniform cross-sectional area. The member has a substantially elliptical shape in an uncompressed state. During installation, the amount of imbalance in the disc pack is measured and a member with an appropriate length is selected and compressed to a substantially circular shape. The compressed member is then placed adjacent the disc pack so that the member expands to compressingly engage an annular recess in the disc pack. The member is preferably installed using an automated dynamic balance correction station as part of a high volume disc drive manufacturing environment.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 09/641,906filed Aug. 18, 2000 which claims priority to U.S. ProvisionalApplication No. 60/150,144 filed Aug. 20, 1999.

FIELD OF THE INVENTION

The present invention relates generally to the field of disc drive datastorage devices, and more particularly, but not by way of limitation, toan automated assembly of a disc drive head-disc assembly which includesan automated dynamic balance correction station.

BACKGROUND

Modem hard disc drives are commonly used in a multitude of computerenvironments ranging from super computers through notebook computers tostore large amounts of data in a form that can be made readily availableto a user. Typically, a disc drive comprises one or more magnetic discsthat are rotated by a spindle motor at a constant high speed. Thesurface of each disc serves as a data recording surface and is dividedinto a series of generally concentric recording tracks radially spacedacross a band between an inner diameter and an outer diameter. The datatracks extend around the disc and data is stored within the tracks onthe disc surface in the form of magnetic flux transitions. The fluxtransitions are induced by an array of transducers otherwise commonlycalled read/write heads. Typically, each data track is divided into anumber of data sectors that store fixed sized data blocks.

Each read/write head includes an interactive element such as a magnetictransducer which senses the magnetic transitions on a selected datatrack to read the data stored on the track. Alternatively, theread/write head transmits an electrical signal that induces magnetictransitions on the selected data track to write data to the track. As isknown in the art, the read/write heads are supported by rotary actuatorarms and are positioned by the actuator arms over a selected data trackto either read or write data. The read/write head includes a sliderassembly having an air-bearing surface that causes the read/write headto fly relative to the disc surface. The air bearing is developed byload forces applied to the read/write head by a load arm interactingwith air currents produced by disc rotation.

Typically, several open-centered discs and spacer rings are alternatelystacked on the hub of a spindle motor, followed by the attachment of aclampring to form a disc pack. The hub, defining the core of the stack,serves to align the discs and spacer rings around a common centerline.Movement of the discs and spacer rings is typically constrained by acompressive load maintained by the clampring. The complementary actuatorarms of an actuator assembly, commonly called an E-block, support theread/write heads to access the surfaces of the stacked discs of the discpack. The read/write heads communicate electronically with a printedcircuit board assembly (PCB) through read/write wires and a flex circuitattached to the E-block. When the E-block is merged with the disc packinto a base deck and a cover is attached to the base deck, a head-discassembly (HDA) is formed. For a general discussion of E-block assemblytechniques, see U.S. Pat. No. 5,404,636 issued to Stefansky, et al. andassigned to the assignee of the present invention.

The head-disc assembly (HDA) of a disc drive is typically assembled in aclean room environment. A clean room environment (free of contaminantsof 0.3 micron and larger) is necessary to ensure that the head-discinterface remains unencumbered and damage free. The slightest damage tothe surface of a disc or read/write head can result in a catastrophicfailure of the disc drive. The primary causes of catastrophic failure,particularly read/write head crashes (a non-recoverable, catastrophicfailure of the disc drive) are generally characterized as contamination,exposure to mechanically induced shock and non-shock induced damage. Thesource of non-shock induced damage is typically traced to the assemblyprocess, and generally stems from handling damage sustained by the discdrive during the assembly process.

Several factors that bear particularly on the problem of assemblyprocess induced damage are the physical size of the disc drive, thespacing of the components, the recording densities sought to be achievedand the level of precision to be maintained during the assembly process.The high levels of precision required by the assembly process arenecessary to attain the operational tolerances required by the discdrive. The rigorous operational tolerances are in response to marketdemands that have driven the need to decrease the physical size of discdrives while simultaneously increasing disc drive storage capacity andperformance characteristics.

Demands on disc drive mechanical components and assembly procedures havebecome increasingly more critical in order to meet the strenuousrequirements of increased capability and size reduction in the face ofthese new market demands. Part-to-part variations in critical functionalattributes in the magnitude of micro-inches can result in disc drivefailures. Additionally, as disc drive designs continue to require sizereduction, smaller read/write heads, thinner substraights, longer andthinner actuator arms, and thinner gimbal assemblies must continue to beincorporated into the drives. This trend significantly exacerbates theneed to improve assembly processes to protect the read/write heads anddiscs from damage resulting from incidental contact between matingcomponents. The aforementioned factors resultantly increase thedifficulty of assembling disc drives, and as the assembly processbecomes more difficult, the need to invent new tools, methods andcontrol systems to deal with the emerging complexities pose uniqueproblems in need of solutions.

Coupled with the size and performance demands is the further marketdriven requirement for, ever increasing fault free performance. Theprogression of continually thinner disc thickness and tighter discspacing, together with increasing track density and increasing numbersof discs in the disc pack, has resulted in a demand for tools, methodsand control systems of ever increasing sophistication. A result has beena decreasing number of assembly tasks involving direct operatorintervention. Many of the tasks involved in modern methods are beyondthe capability of operators to reliably and repeatedly perform, furtherdriving the need for automated equipment and tooling.

In addition to the difficulties faced in assembling modem disc drives ofhigh capacity and complex, physical product performance requirementshave dictated the need to develop new process technologies to ensurecompliance with operating specifications. The primary factors drivingmore stringent demands on the mechanical components and the assemblyprocess are the continually increasing areal densities and data transferrates of the disc drives.

The continuing trend in the disc drive industry is to develop productswith ever increasing areal densities, decreasing access times andincreasing rotational speeds. The combination of these factors placesgreater demands on the ability of modem servo systems to control theposition of read/write heads relative to data tracks. The ability toassemble HDAs nominally free from the effects caused by unequal loadforces on the read/write heads, disc pack imbalance or one of thecomponents of runout, velocity and acceleration (commonly referred to asRVA) poses a significant challenge as track densities increase. Thecomponents of RVA are disc runout (a measure of the motion of the discalong the longitudinal axis of the motor as it rotates); velocity (ameasure of variations in linear speed of the disc pack across thesurface of the disc); and acceleration (a measure of the relativeflatness of the discs in the disc pack). By design, a disc drivetypically has a discreet threshold level of resistance to withstandrotationally induced noise and instability, below which the servo systemis not impaired. Also, a fixed range of load forces must be maintainedon the read/write head to ensure proper fly height for data exchange.The operating performance of the disc drive servo system is affected bymechanical factors beyond the effects of mechanically induced read/writehead oscillation from disc surface anomalies. Errors are traceable todisc pack imbalance and RVA noise sources. Even with improved approachesto the generation of position error signals in the disc drive servosystem, the ability of the system to deal with such issues is finite.The limits of the servo system capability to reliably control theposition of the read/write head relative to the data track must not beconsumed by the noise present in the HDA resulting from the assemblyprocess. Consumption of the available margin by the assembly processleaves no margin in the system to accommodate changes in the disc driveattributes over the life of the product. An inability to accommodatechanges in the disc drive attributes leads to field failures and anoverall loss in product reliability, a detrimental impact to productmarket position.

Thus, in general, there is a need for an improved approach to discdrive-assembling technology to minimize the potential of damage duringassembly, to produce product that is design compliant and reliable, andto minimize mechanically induced system noise. One such need is that ofan automated dynamic balance correction of a disc drive.

SUMMARY OF THE INVENTION

An automated dynamic balance correction station used to produce balancecorrected disc drive assemblies by placing a balance correction memberon disc packs displaying an out of balance condition. The balancecorrection station has a conveyor, a lift and balance measure assembly,a lift and locate assembly, a feature detection assembly and a balancecorrect assembly. The disc drive assembly includes a disc pack that hasa spindle motor with an attached spindle motor hub that has a timingmark and supports a stack of interleaved member parts. The stackedmember parts include discs, spacer rings and enlarged stack ringsconstrained by a clampring that has an annular balance correctioncontainment cavity.

The disc drive is moved via the conveyor to the lift and balance measureassembly where the disc pack is lifted and activated to operationalspeed. At operational speed the lift and balance measure assembly checksfor and measures, if present, the amount of imbalance present in thedisc pack. If imbalance is present, the dynamic balance correctionstation determines the angular position of the source of the imbalancerelative to the timing mark. Using the feature detection assembly todetermine the angular placement position for the balance correctionmember relative to the timing mark and using the balance correctassembly to physically place the balance correction member on the discpack, the dynamic balance correction station dispenses the balancecorrection member into the annular balance correction containment cavityto form a balance corrected disc pack.

The balance correction member comprises a C-shaped ring formed from awire of nominally uniform cross-sectional area and has a substantiallyelliptical shape in an uncompressed state. The balance correct assemblycompresses the balance correction member to a substantially circularshape and then places the compressed balance correction member adjacentthe disc pack so that the compressed balance correction member expandsand compressingly engages an annular recess in the disc pack.

These and other features and advantages which characterize the presentinvention will be apparent from a reading of the following detaileddescription and a review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top, partially cutaway view of a disc drive of the type thatis assembled by an automated disc drive assembly incorporating a dynamicbalance correction station constructed in accordance with the presentinvention.

FIG. 2 is an elevational view of the spindle motor of the disc drive ofFIG. 1 having a plurality of discs and spacers mounted and securedthereon via a clampring to form a disc pack.

FIG. 3 is a partial cutaway, elevational view of a balance correcteddisc pack with a cross-sectional view of the clampring and installedbalance correction member.

FIG. 4 is a perspective view of the balance correction member andclampring of FIG. 3.

FIG. 5 is a partial elevational, sectional view of the clampring of FIG.4 showing one of the mating fasteners securing the clampring to thespindle motor hub.

FIG. 6 is an exploded perspective view of a dynamic balance correctionstation constructed in accordance with the present invention andutilized to install the clampring of FIG. 4 to the disc pack of FIG. 3.

FIG. 7 is a perspective view of a pick and place manipulator assembly ofthe balance correction station of FIG. 6

FIG. 8 is an exploded perspective view of a component capture andtransfer assembly of the balance correction station of FIG. 6

FIG. 9 is a cross-sectional view of an end effector of the pick andplace manipulator assembly of FIG. 7.

FIG. 10 is a plan view of the balance correction member of FIG. 3 inboth an uninstalled configuration and a portion of one half of thebalance installed balance correction member in an installedconfiguration (shown in dashed lines).

DETAILED DESCRIPTION

Referring to the drawings in general, and more particularly to FIG. 1,shown therein is a top view of a disc drive 100 constructed inaccordance with the present invention. The disc drive 100 includes abasedeck 102 to which various disc drive components are mounted, and atop cover 104 (shown in part) which together with the basedeck 102provides a sealed internal environment for the disc drive 100. Numerousdetails of construction of the disc drive 100 are not included in thefollowing description as such are well known to those skilled in the artand are believed to be unnecessary for the purpose of describing thepresent invention.

Mounted to the basedeck 102 is a spindle motor 106 to which severaldiscs 108 are mounted on a spindle motor hub 109 and secured by aclampring 110 for rotation at a constant high speed. In addition toproviding support for the stacked discs 108, the spindle motor hub 109also provides a timing mark 111 used during the assembly process toreference the angular location of a source of rotational imbalance.Adjacent the discs 108 is an actuator assembly 112 (also referred to asan “E-block”) which pivots about a cartridge bearing 114 in a rotaryfashion. The actuator assembly 112 includes actuator arms 116 (only oneshown) that support load arms 118. Each load arm 118 in turn supportsread/write heads 120, with each of the read/write heads 120corresponding to a surface of one of the discs 108. As mentioned, eachof the discs 108 has a data recording surface divided into concentriccircular data tracks, and the read/write heads 120 are positionablylocated over data tracks to read data from, or write data to, thetracks.

The actuator assembly 112 is controllably positioned by a voice coilmotor assembly (VCM) 122, comprising an actuator coil 124 immersed inthe magnetic field generated by a magnet assembly 126. A latch assembly128 latches the actuator assembly in a predetermined park position whenthe disc drive 100 is turned off. A magnetically permeable flux path isprovided by a steel plate 130 (also called a pole piece) is mountedabove the actuator coil 124 to complete the magnetic circuit of the VCM122.

When controlled DC current is passed through the actuator coil 124, anelectromagnetic field is set up which interacts with the magneticcircuit of the VCM 122 to cause the actuator coil 124 to move relativeto the magnet assembly 126 in accordance with the well-known Lorentzrelationship. As the actuator coil 124 moves, the actuator assembly 112pivots about the cartridge bearing assembly 114, causing the heads 120to move over the surfaces of the discs 108 thereby allowing the heads120 to interact with the data tracks of the discs 108.

To provide the requisite electrical conduction paths between the heads120 and disc drive read/write circuitry (not shown), read/write headwires (not separately shown) are routed on the actuator assembly 112from the heads 120 along the load arms 118 and the actuator arms 116 toa flex circuit 132. The read/write head wires are secured tocorresponding pads of a flex circuit printed circuit board (PCB) 134 ofthe flex circuit 132. The flex circuit 132 is connected to a flexcircuit bracket 136 in a conventional manner, which in turn is connectedthrough the basedeck 102 to a disc drive PCB (not shown) mounted to theunderside of the basedeck 102. The disc drive PCB provides the discdrive read/write circuitry which controls the operation of the heads120, as well as other interface and control circuitry for the disc drive100.

To maintain the sealed internal environment for the disc drive 100, aseal gasket 138 is molded onto the top cover 104. Top cover 104 has aplurality of gasket attachment apertures 140 through which gasketmaterial flows during the gasket molding process. A continuum ofsymmetrically formed gasket material is disposed on both the top andbottom surfaces of the top cover 104 and injected through the apertures140. During the cure process, the gasket material injected into thegasket attachment apertures 140 bonds the portion of the seal gasketadjacent the top surface of the top cover to the portion of the sealgasket adjacent the bottom portion of the top cover 104, thereby sealingthe gasket attachment apertures 140 and forming the seal gasket 138. Agasket material found to be useful for this application is FLUOREL bythe 3 M company, and more specifically, 3M FLUOREL, FE-5621Q.

Shown in FIG. 2 is a disc pack 142 which includes alternately stackeddiscs 108 and spacer rings 144 in the manner of a traditional disc packon the spindle motor hub 109. The spindle motor hub 109 is attached tothe spindle motor 106 via a motor housing 150 which supports an outerrace 152, where the motor housing 150 and outer race 152 together spinfreely around a stationary threaded shaft 154 by interior rollerbearings (not shown) therebetween.

Upon completing the stacking of discs 108 interleaved with the spacerrings 144, with the last stacked component typically being the top disc108, the clampring 110 is secured to the spindle motor hub 109 by thehardware pieces or fasteners 156. The spindle motor hub 109 provides acomponent-mounting surface (not separately shown) containing anappropriate number of attachment apertures (not specifically shown) witheach fastener 156 engaging one attachment aperture to secure theclampring 110 to the spindle motor hub 109, thereby completing the discpack 142.

While constructing the disc pack 142, the first component placed on thespindle motor hub is usually one of the discs 108. However, as shown byFIG. 3 the last stacked part that is placed on the spindle motor hub 109can be an enlarged spacer ring 146 rather than a disc. The enlargedstack ring 146 has a diameter substantially equal to that of the spacerrings 144 and a thickness substantially equal to the sum of thethickness of the spacer ring 144 plus the thickness of the disc 108.Whether the last stacked part is a disc or the enlarged stack ring 146,the clampring 110 imparts a clamping force on the top surface of thelast stacked member. The applied clamp force secures the discs 108 ofthe disc pack 142 in a fixed position for the operational life of discdrive 100. Additionally, FIG. 4 shows a balance correction member 158confined within an annular balance correction containment cavity 160 inthe clampring 110. Proper placement of the balance correction member 158within an annular balance correction containment cavity 160 results inthe formation of a balance corrected disc pack 161.

FIG. 4 provides an illustration of the balance correction member 158which is a C-shaped wire-ring and other wise referred to herein as abalance correction C-shaped wire-ring 158. To assure shape retention andto instill a spring action response to externally applied forces, thebalance correction member 158 is made from full hard 302 stainless steelwire.

As shown in FIG. 4, the clampring 110 has a central bore 159, theannular balance correction containment cavity 160 and six hardware ports162 which extend through the clampring 110 symmetrically about thecentral bore 159. A compressive force distribution surface 164, a reliefsurface 166 and a step portion 168 are provided as shown. Each hardwareport 162 directly corresponds to attachment apertures (not separatelyshown) in the spindle motor hub 109, and each of the fasteners 156 isdisposed to extend through one of the hardware ports 162. The forcedistribution surface 164 is elevated above the relief surface 166 by thestep portion 168. The step portion 168 has a thickness of about 0.006inches. By simultaneously applying a final torque to the fasteners 156during the assembly process, the force distribution surface 164 levelsthe compressive load across the clampring to assure the surface of thedisc 108 remains distortion free.

FIG. 5 shows one of the fasteners 156 that secure the clampring 110 tothe spindle motor hub 109. Each fastener 156 has a contact surface 170and a thread engagement portion 172. Also, FIG. 5 shows thecross-sectional geometry of the annular balance correction containmentcavity 160. During the assembly process the balance correction member 58is placed into a compressed mode while being inserted into the mouth ofthe annular balance correction containment cavity 160. Upon entry intothe mouth of the annular balance correction containment cavity 160, thebalance correction member 158 expands, driving the balance correctionmember 158 to the base of the annular balance correction containmentcavity 160. The base of the annular balance correction containmentcavity 160 confines the balance correction member 158 and prevents thebalance correction member 158 from attaining its free state form,thereby holding the balance correction member 158 in a compressed mode.By holding the C-shaped wire-ring in a compressed state the annularbalance correction containment cavity 160 prevents movement of thebalance correction member 158.

As disclosed above, each one of the fasteners 156 directly correspondsto one of the hardware ports 162. The thread engagement portion 172 ofeach of the fasteners 156 passes through the corresponding hardware port162 to engage an attachment aperture. Upon simultaneous application of afinal torque force on each fastener 156, the contact surface 170 of thefastener 156 contacts the force distribution surface 164 and imparts acompressive force on the force distribution surface 164 while beingprevented from making contact with the relief surface 166. By confiningthe contact surface 170 to engagement with the force distributionsurface 164 as the means of imparting the simultaneously appliedcompressive load developed by the finally applied torque force, therunout, velocity, and acceleration (RVA) characteristics remain withinthose limits required by disc drive 100.

Runout of the discs 108 is a measure of the axial variation of theheight of the disc 108 surface around a circumferential arc of aspecific radius. The velocity component is a measure of the rate ofchange of the axial displacement of the surface of the disc 108 around acircumferential arc of a specific radius. The acceleration component ofRVA is a measure of the rate of change of the velocity of disc 108around a circumferential arc of a specific radius.

FIG. 6 provides a more clear view of the associated components of thebalance correction station 200 used in the production of balancecorrected disc drives 100. As shown by FIG. 6, a frame 202 supports aplurality of tooling assemblies used during the process of attaching thebalance correction member 158 (FIG. 4) to the disc pack 142 (FIG. 2).Included in FIG. 6 is a conveyor 204 with an attached lift and balancemeasurement assembly 206 along with an attached lift and locate assembly208. The conveyor 204, attached to the frame 202, is first used toconvey disc packs 142 awaiting balance measurement into the balancecorrection station 200. The lift and balance measure assembly 206 isused to measure the amount of imbalance present in the disc packassembly 142.

For disc packs 142 that are measured and found to be within thetolerance range of acceptability for imbalance, the conveyor 204transfers those disc packs 142 from the balance correction station 200to other processing equipment. For disc packs 142 that display an amountof imbalance beyond the correction capabilities of the balancecorrection station 200, the conveyor 204 transfers the from the balancecorrection station 200 to be reworked or discarded. For each disc pack142 identified by the lift and balance measure assembly 206 as beingoutside the imbalance tolerance specifications, but within thecorrection capabilities of the balance correction station 200, theconveyor 204 transfers the disc pack 142 to the lift and locate assembly208.

The lift and locate assembly 208 positions the disc pack 142 to assurethat both a feature detection assembly 210 and a balance correctedassembly 212 have access to the disc pack 142. The balance correctassembly 212 utilizes a baseplate 214 to provide the controllable,common mounting plane for several component feeder assemblies 216 (alsoreferred to herein as vibratory rod component feeder assemblies), a pickand place manipulator assembly 218 and a component capture and transferassembly 220. In FIG. 6 three such vibratory rod component feederassemblies 216 are shown. Each of the component feeder assemblyassemblies 216 is used to dispense a specific geometric configuration ofthe balance correction members 158, that is, the C-shaped wire-rings.The component capture and transfer assembly 220 is positionable beneathany selected one of the component feeder assembly assemblies 216. Thecomponent capture and transfer assembly 220 receives the balancecorrection members 158 dispensed by the component feeder assemblyassemblies 216.

Upon receipt of the balance correction member 158, the component captureand transfer assembly 220 transfers the balance correction member 158 tothe pick and place manipulator assembly 218. The pick and placemanipulator assembly 218 picks the balance correction member 158 fromthe component capture and transfer assembly 220 and proceeds to placethe balance correction member 158 on the disc pack 142.

Also illustrated in FIG. 6 is a clean room automation technicianoperational status light pole 222. The status light pole 222 provides aquick reference regarding the status of the balance correction station200 at any time during operation of the balance correction station 200.The status light pole 222 has a number of colored lamps or lenses. Onecolor is selected to signify that the balance correction station 200 isprogressing in a typical manner and processing disc packs 142unencumbered. A second color is selected to signify that the balancecorrection station 200 is inoperative and available for receiving andprocessing disc packs 142. A third color is selected to signify that thebalance correction station 200 has encountered difficulty whileprocessing the disc pack 142. This arrangement permits a clean roomtechnician to monitor the status of the balance correction station at aglance. A station control computer 224 controls elimination of thestatus lights of the status light pole 222.

The station control computer 224 is mounted in the base portion of theframe 202. The station control computer 224 provides digital control andcommunication with the conveyor 204, the lift and balance measureassembly 206, the lift and locate assembly 208, the feature detectionassembly 210 and the balance correct assembly 218. It will be noted thatthe feature detection assembly 210 has two primary assemblies. The firstassembly is a downward focusing digital recognition assembly 226 and thesecond assembly is an upward focusing digital recognition assembly 228.

A first C-clamp camera attachment member 230 secures the downwardfocusing digital recognition assembly 226. A second C-clamp cameraattachment member 232 secures the upward focusing digital recognitionassembly 228. The first C-clamp camera attachment member 230 is securedto a downward focusing vision system mounting plate 234, which in turnis attached to the frame 202. The second C-clamp camera attachmentmember 232 is attached to an upward focusing vision system mountingplate 236 which in turn is attached to the frame 202. In order to ensureconsistency in quality of image information gathered by the featuredetection assembly 210, both the downward focusing digital recognitionassembly 226 and the upward focusing digital recognition assembly 228are provided with dedicated light sources. A light source 238 isattached to the first C-clamp camera attachment member 230 to providethe illumination required by the downward focusing digital recognitionassembly 226, and a second light source 240 is attached to the secondC-clamp camera attachment member 232 to provide the illumination neededby the upward focusing digital recognition assembly 228.

The downward focusing digital recognition assembly 226 includes a firstdigital video camera 242, a first signal cable 244 and a first digitalvideo capture board 246. The first signal cable 244 attaches the firstdigital video camera 242 to the first video capture board 246. Theupward focusing digital recognition assembly 228 includes a seconddigital video camera 248, a second signal cable 250 and a second digitalvideo capture board 252. The second signal cable 250 attaches the seconddigital video camera 248 to the second digital video capture board 252.Each of the digital video capture boards 246 and 252 contains patternrecognition software internal to the station control computer 224.

Included in the pick and place manipulator assembly 218 of FIG. 7 is amanipulator mounting assembly 254 that has an attachment plate 256, apair of manipulator clamp bars 258, a pair of centering jack blocks 260,several custom manipulator arm screws 262 and a number of hardwareattachment fasteners 264. The attachment plate 256 provides a mountingsurface as well as a reference plane to the balance of the components ofthe pick and place manipulator assembly 218.

The manipulator clamp bars 258 are connected to the attachment plate 256by the custom manipulator arms screws 252. The manipulator clamp bars258 rest on the base plate 214 of the balance correction assembly 212.The centering jack blocks 260 are attached to the attachment plate 256by the attachment fasteners 264. The centering jack blocks 260 are usedto both center the pick and place manipulator assembly 218 relative tothe base plate 214 of the balance correction assembly 212 and to securethe pick and place manipulator assembly 218 to the balance correctassembly 212. The custom manipulator arms screws 252 are configured toallow adjustments for the pitch of a rotary actuator assembly 266relative to the disc pack 142 held by the lift and locate assembly 208.

The attachment plate 256 serves as the attachment surface for the rotaryactuator assembly 266, which has two primary components. The first is amotion controller 268 attached directly to the attachment plate 256 andthe second component is a rotary stepper motor 270 connected to themotion controller 268. The rotary stepper motor 270 provides amanipulator arm 272 an ability to travel along on an arcuate path in theX-Y plane. The motion controller 268 controls both the speed that themanipulator arm 272 traverses through X-Y plane and the ability of themanipulator arm 272 to repeatedly stop accurately at particular pointsalong the arcuate path.

Attached to the rotary stepper motor 270 is the manipulator arm 272having attached thereto an end effector receiving plate 274 to which anend effector assembly 276 is attached. The manipulator arm 272 definesin initial Z-axis position of the end effector assembly 276, as well asthe radius of the arcuate path traveled by the end effector assembly276. During the operation of the balance correction station 200, thearcuate path traveled by the end effector 267 assures that the endeffector assembly 276 communicates with both a disc pack assembly 142and the component capture and transfer assembly 220.

Included in FIG. 8 is a linear actuator 278 that provides the linearmotion required by the component capture and transfer assembly 220 toservice each of the several component feeder assembly assemblies 216during the operation of the balance correction station 200. FIG. 8further illustrates a positioning plate 280 that is slidingly attachedto the linear actuator 278. The positioning plate 280 serves as anattachment host and linear travel vehicle for the remaining componentsof the component capture and transfer assembly 220. Also shown by FIG. 8are a transition plate 282 attached to the position plate 280, aflexible cable-way 284 attached to the transition plate 282, a grippermount plate 286 attached to the transition plate 282, a cover 287attached to the gripper mount 286, a ring expanding gripper assembly 288attached to the gripper mount 286 and a pair of sensor mounts 289attached to the gripper mount 286.

The mounting hole pattern (not shown) of the ring expanding gripperassembly 288 is not the same as the mounting hole pattern (not shown) ofthe positioning plate 280. As such, the transition plate 282 provides anappropriate mounting hole pattern (not shown) for attaching thetransition plate 282 to the positioning plate 280. The transition plate282 further provides a hole pattern (not shown) for attaching thegripper mount plate 286 to the transition plate 282. The gripper mountplate 286 provides the ability to adjust the pitch of the ring expandinggripper assembly 288 to be consistent with the pitch of the end effectorassembly 276. The sensor mounts 289 the structure for mounting sensors(not shown) that detect the presence of the end effector assembly 276while the cover 287 contributes to the maintenance of the clean roomenvironment by containing particulate generation that occurs during theoperation of the balance correction station 200.

FIG. 8 further shows the primary components of the ring expandinggripper assembly 288 including the gripper base 290 which is attached tothe gripper mount plate 286. The gripper base 290 supports severalgripper sections 292, the number of gripper sections 292 being afunction of the particular component handled by the balance correctionstation 200. In FIG. 8, the number of gripper sections 292 is four asdetermined by the configuration of the balance correction member 158.Each of the gripper sections 292 is slidingly mounted to the gripperbase 290 and attached to a pneumatic cylinder 294. The gripper sections292 provide the ring expanding gripper assembly 288 the ability to forma variable diameter annular balance correction containment cavity 293.

During operation of the balance correction station 200, the mostprominent diameters for the variable diameter annular balance correctioncontainment cavity 293 are the maximum diameter and the minimumdiameter. The maximum diameter of the variable diameter annular balancecorrection containment cavity 293 is defined when the pneumatic cylinder294 is at maximum stroke in a first direction.

The minimum diameter annular balance correction containment cavity 293is defined when the pneumatic cylinder 294 is at maximum stroke in asecond and opposite direction from that of the first maximum strokeposition.

Slidingly attached to each of the other gripper sections 292 is aspring-loaded retractable component containment member 295. Collectivelythe spring-loaded retractable component containment members 295 form acontainment wall (not separately shown) of the variable diameter annularbalance correction containment cavity 293.

In cooperating with the end effector assembly 276 during the transfer ofthe balance correction member 158, the spring-loaded retractablecomponent containment members 295 yield to the end effector assembly276. By yielding, the spring-loaded retractable component containmentmembers 295 allow the balance correction member 158 to expand slightlyand pressingly engage the end effector assembly 276.

Returning to FIG. 7, the end effector assembly 276 has three maincomponents: a Z-axis air slide 296, an angle plate 298 and an endeffector 300. The Z-axis air slide 296 provides the coupling between theend effector receiving plate 274 and the second primary component theangle plate 298. Additionally, the Z-axis air slide 296 facilitates thevertical travel required by the end effector 300 during the operation ofthe balance correction station 200. The angle plate 298 provides thestructure for attaching the third primary component of the end effectorassembly 276, the end effector 300.

A detailed view of the mechanics of the end effector 300 is shown inFIG. 9. Included in FIG. 9 is a view of the angle plate 298, an outerrace clamp 302 attached to the angle plate 298, a motor hub bearingassembly 304 with an inner race 306 and an outer race 308 disposedwithin the end effector 300 to bring the outer race 308 into pressingengagement with the outer race clamp 302. The inner race 306 is inpressing engagement with a motor hub 310. The motor hub bearing assembly304 provides the ability of the motor hub 310 to rotate freely inrelation to the angle plate 298. FIG. 9 also shows a rotary indexingmotor 312 with an attached rotatable shaft 314. The rotatable shaft 314is held in compressive engagement with the motor hub 310 by a hub clamp316. In addition to engaging the outer race clamp 302, the outer race308, of the motor hub bearing assembly 304, engages the angle plate 298,while the inner race 306 of the motor hub bearing assembly 304 engages acylindrical plunger housing 318. As shown, the cylindrical plungerhousing 318 is attached to the motor hub 310 by shoulder screws 320.

The internal wall of the cylindrical plunger housing 318 has acylindrical plunger retention member 322, which retains a cylindricalplunger 324. The cylindrical plunger 324 has a retention groove 326 thatengages the retention in member 322 of the cylindrical plunger housing318. FIG. 9 also shows a spring-loaded centering shaft 330 protrudingthrough the center portion of the cylindrical plunger 324. Thespring-loaded centering shaft 330 is used to center the disc pack 142during the operation of the automation distress assembly station 200.The stability of the spring-loaded centering shaft 330 is maintained bythe plurality of alignment bearing assembly 332.

Enclosing a portion of the outer wall of the cylindrical plunger housing318 is a plunger compression spring 334 which maintains slidingclearance with the outer wall of the cylindrical plunger housing 318. Inaddition to the plunger compression spring 334 being adjacent the outerwall of the cylindrical plunger housing 318, a plunger bearing assembly336 maintains sliding engagement with the outer wall of the cylindricalplunger housing 318. The outer race of the plunger bearing assembly 336maintains pressing contact with a component retainer 338. The plungerbearing assembly is used to promote minimal drag between the componentretainer 338 and the cylindrical plunger housing 318 as the componentretainer 338 slides along the cylindrical plunger housing 318 during theoperation of the balance correction station 200. The component retainer338 also provides a locker ring retainer groove 340 that confines alocking ring 342.

The locking ring 342 serves a dual purpose. The first purpose forinclusion of the locking ring 342 within the end effector 300 is torestrict the movement of the plunger bearing assembly 336 during theoperation of the balance correction station 200. The second is toprovide a land for the compression spring 334. The compression spring334 imparts a compressive load needed to ensure proper functioning ofthe end effector 300 during operation of the balance correction station200, and the locking ring 342 facilitates the load absent damage to theplunger bearing assembly 336. The plunger compression spring 334 permitstravel of the component retainer 338 in the direction of the shoulderscrews 320, whereas the cylindrical plunger 324 restricts travel of thecomponent retainer 338 when the cylindrical plunger 324 in moving in adirection away from the shoulder screws 320.

To maintain a clean environment in the clean room during the operationof the balance correction station 200, two additional components of theend effector 300 are shown in FIG. 9. A vacuum housing 344 is attachedto the angle plate 298 which in conjunction with a vacuum line (notshown), provides a channel for removal of all particulate mattergenerated in and around the component retainer 338 during operation ofthe balance correction station 200. Similarly, a motor cover 346 inconcert with another vacuum line (not shown) provides a channel andmethod for removal of particulate matter generated by the rotaryindexing mortar 312 and the components associated with the rotaryindexing mortar 312. The removal of the generated particulate matter isongoing during the operation of the balance correction station 200.

Turning to FIG. 10, the final installed shape of the balance correctionmember 158 is circular. The uninstalled shape is approximatelyelliptical. The elliptical initial shape is determined by the followingmethod. A linear load distribution that meets the following conditionswas applied to a circular ring solution for one half of the balancecorrection C-shaped wire-ring 158, that is where:

ω=Aθ+B  (Equation 1)

Where A and B are constants the load ω 350 is linear at any pointlocated at angle θ, measured from a center point 352, at 0⁰, along thepath of the balance correction member 158 between center point 352 andend point θ₁ 354. FIG. 10 further shows θ₁ 354 as an angle measured froma center point 352 of the balance correction member 158 to an end point356 of the balance correction member 158 encompassing one half of thebalance correction member 158 where the following equation holds:$\begin{matrix}{{{\frac{2}{\theta_{1}}\sin \quad \theta_{1}} - {2B\quad \sin \quad \theta_{1}} + \frac{2\quad \cos \quad \theta_{1}}{\theta_{1}^{2}} - {\frac{2B}{\theta_{1}}\cos \quad \theta_{1}} + {B\quad \sin \quad \theta_{1}} - \frac{2\quad}{\theta_{1}^{2}} + \frac{2B}{\theta_{1}}} = 0} & \left( {{Equation}\quad 2} \right)\end{matrix}$

Solving for B, the following equation is obtained: $\begin{matrix}{B = \frac{{\frac{- 2}{\theta_{1}}\sin \quad \theta_{1}} + \frac{2}{\theta_{1}^{2}} - \frac{2\quad \cos \quad \theta_{1}}{\theta_{1}^{2}}}{{{- 2}\quad \sin \quad \theta_{1}} - {\frac{2}{\theta_{1}}\cos \quad \theta_{1}} + {\sin \quad \theta_{1}} + \frac{2}{\theta_{1}}}} & \left( {{Equation}\quad 3} \right)\end{matrix}$

Equation 3 can be substituted into equation 2 and solved for A. With Aand B known, a FEM (Finite Element Analysis) model can be created for acircular ring with the load applied as described above. The solution ofthe FEM model will give the initial shape.

The mass of the balance correction member 158 needed to overcome anamount of imbalance present in the disc pack 142 is determined by theover length of the balance correction C-shaped wire-ring 158, hence θ₁is determined by the amount of imbalance that needs to be produced bythe balance correction member 158. Computer generated empirical data hasshown the total load requirement of the ring to stay in place duringvertical shock is 2 lbs. or for one half the ring (1 lb.). In solvingfor the load for one half the ring where the load ω is linear with angleθ the equation is: $\begin{matrix}{{1\quad {{lb}.}} = {\int_{0}^{\theta_{1}}{\omega {\theta}}}} & \left( {{Equation}\quad 4} \right)\end{matrix}$

Substituting equation 1 for ω the equation becomes: $\begin{matrix}{{{\int_{0}^{\theta_{1}}{\left( {{A\quad \theta} + B} \right){\theta}}} = {{\frac{1}{2}A\quad \theta_{1}^{2}} + {B\quad \theta_{1}\quad {and}}}}{A = \frac{2 - {2B\quad \theta_{1}}}{\theta_{1}^{2}}}} & \left( {{Equation}\quad 5} \right)\end{matrix}$

The sum of the forces in the Y direction must be zero for staticequilibrium, therefore the equation is: $\begin{matrix}{{\int_{0}^{\theta_{1}}{\omega \quad \cos \quad \theta {\theta}}} = 0} & \left( {{Equation}\quad 6} \right)\end{matrix}$

Substituting equation 1 for ω the equation becomes: $\begin{matrix}{{\int_{0}^{\theta_{1}}{\left( {{A\quad \theta \quad \cos \quad \theta} + {B\quad \cos \quad \theta}} \right){\theta}}} = \quad {0 = {\left. {{A\quad \theta \quad \sin \quad \theta} + {A\quad \cos \quad \theta} + {B\quad \sin \quad \theta}} \right\rbrack_{0}^{\theta_{1}}\quad = \quad {0\quad {{= \quad {{{A\quad \theta_{1}\quad \sin \quad \theta_{1}} + {A\quad \cos \quad \theta_{1}} + {B\quad \sin \quad \theta_{1}} - A} = 0}}}}}}} & \left( {{Equation}\quad 7} \right)\end{matrix}$

Substituting equation 3 for A, the equation can be solved for B andbecomes: $\begin{matrix}{{{\frac{2 - {2B\quad \theta_{1}}}{\theta_{1}^{2}}\theta_{1}\quad \sin \quad \theta_{1}} + \quad {\frac{2 - {2B\quad \theta_{1}}}{\theta_{1}^{2}}\cos \quad \theta_{1}} + {B\quad \sin \quad \theta_{1}} - \frac{2 + {2B\quad \theta_{1}}}{\theta_{1}^{2}}} = 0} & \left( {{Equation}\quad 8} \right)\end{matrix}$

Operation

The station control computer 224 of FIG. 6, used for process managementand control, signals the conveyor 204 of FIG. 6 that responds byconveying a disc pack 142 of FIG. 2 into the balance correction station200 of FIG. 6 to begin processing the disc pack 142. First, the discpack 142 is positioned into the lift and balance measure assembly 206 ofFIG. 6 to measure the amount and location of imbalance present in thedisc pack and, if imbalance is present, report the location of theimbalance relative to the timing mark 111 of FIG. 1 of the disc pack 142to the station control computer 224. To make the required measurements,the lift and balance measure assembly 206 activates the spindle motor106 of FIG. 1 to accelerate the disc pack 142 to its operationalvelocity. When the operational velocity is achieved, measurements aretaken using traditional balance measurement instruments.

If the imbalance present in the disc pack 142 is within an acceptabletolerance level no additional processing will be performed on the discpack 142 and the disc pack 142 will be returned to the conveyor 204 tobe transported out of the balance correction station 200. If theimbalance present in the disc pack 142 exceeds the correction ability ofthe balance correction station 200 no additional processing will beperformed on the disc pack 142 and the disc pack 142 will be returned tothe conveyor 204 to be transported out of the balance correction station200. If the imbalance present in the disc pack 142 exceeds the tolerancelevel, but remains with the correction ability of the balance correctionstation 200, the disc pack 142 will be placed on the conveyor 204 andtransported to the lift and locate assembly 208 of FIG. 4.

The lift and locate assembly 208 positions the disc pack 142 for receiptof a balance correction member 158. The balance correction station 200has a number of varying mass balance correction members 158 from whichto select. The specific balance correction member 158 selected dependson the amount of mass required to counteract the imbalance present inthe disc pack 142. The general configuration, of each type of balancecorrection member 158 is a C-shaped wire-ring. The length of wire usedto form the balance correction member 158 determines the amount of masspresent in each type of balance correction member 158. The greater thelength of wire in the balance correction member 158, the greater themass of the balance correction member 158. And conversely, the shorterthe length of wire in the balance correction member 158, the less themass of the balance correction member 158. Having identified the propermass to be added to the disc pack 142, the automated disc drive assemblystation 200 selects one of the plurality of component feeder assemblyassemblies 216 of FIG. 4 as each contains a different weighted balancecorrection member 158.

The feature detection assembly 210 of FIG. 4 locates the gap portion ofthe C-shaped wire-ring and the position of the timing mark 111 on thespindle motor hub 109. The feature detection assembly 210 includes adownward focusing digital video camera 242 of FIG. 4 and an upwardfocusing digital video camera 248 of FIG. 4. The downward focusingdigital camera 242 is stationary and focused to record an electronicimage of the angular position of the timing mark 111 after the lift andlocate assembly 208 positions the disc pack 142 for receipt of a balancecorrection member 158.

Having determined the proper balance correction member 158, the stationcontrol computer 224 activates the balance correct assembly 218 of FIG.4 which responds by aligning the component capture and transfer assembly220 of FIG. 4 beneath the component feeder assembly 216 containing thebalance correction member 158 of proper mass. With the component captureand transfer assembly 220 in position, the station control computersignals the component feeder assembly 216 to dispense the balancecorrection member 158 into the variable diameter annular balancecorrection containment cavity 293 of FIG. 8. Four spring loaded grippersections 292 of FIG. 8 on the gripper base 290 of FIG. 8 define thevariable diameter annular balance correction containment cavity 293.While awaiting receipt of the balance correction member 158, the fourspring loaded gripper sections 292 define the maximum diameter of thevariable diameter annular balance correction containment cavity 293.Upon receipt of the balance correction member 158, the four springloaded gripper sections 292 move together to from the minimum diameterof the variable diameter annular balance correction containment cavity293, the movement slightly collapses the diameter of the balancecorrection member 158 to allow transfer of the balance correction member158 to the pick and place manipulator assembly 218 of FIG. 7.

With the balance correction member 158 secured, the balance correctassembly 218 transports the balance correction member 158 from beneaththe component feeder assembly 216 into alignment with the pick and placemanipulator assembly 218. Then the station control computer 224activates the pick and place manipulation assembly 218 which responds byactivating the rotary stepper motor 270 of FIG. 7 to position the endeffector assembly 276 of FIG. 7 above the balance correction member 158.With the end effector assembly 267 positioned for pick up, the stationcontrol computer 224 signals the Z-axis air slide 296 of FIG. 7 of theend effector assembly 276 to place the end effector 300 of FIG. 7 inmating contact with the four spring loaded gripper sections 292 anddepress the four spring loaded gripper sections 292.

At the bottom of the stroke of the Z-axis air slide 296, the endeffector 300 depresses the four spring loaded gripper sections 292 to aposition below the plane containing the balance correction member 158.With the gripper sections below the balance correction member 158 thebalance correction member 158 is allowed to expand slightly and come torest in pressing engagement with a component retainer 338 of FIG. 9 ofthe end effector 300 and adjacent a cylindrical plunger 324 of FIG. 9 ofthe end effector 300. With the balance correction member 158 secured bythe end effector 300, the Z-axis air slide 296 returns the end effector300 to the home position and the rotary stepper motor 270 re-positionsthe end effector assembly 276 above the upward focusing digital camera248.

The upward focusing digital camera 248 records and reports to thestation control computer 224 the position of the gap between the ends ofthe C-shaper wire-ring of the balance correction member 158, relative tothe location of the timing mark 111 of the disc pack 142. Based on therelative positional information of the imbalance source, the timing mark111 and the gap between the ends of the C-shaped wire-ring, the stationcontrol computer 224 determines the placement position of the balancecorrection member 158 within the disc pack 142. Once the placementposition of the balance correction member 158 is determined, the stationcontrol computer 224 signals a rotary indexing motor 312 of FIG. 9 ofthe end effector 300 to rotate the position of the balance correctionmember 158. When the gap between the ends of the C-shaped wire-ring ofthe balance correction member 158 is positioned to assures the mass ofthe balance correction member 158 is correctly positioned to offset theimbalance present in the disc pack 142, the rotation stops.

Next the balance correction member 158 is placed in an annular balancecorrection containment cavity 160 of FIG. 3 of a clampring 110 of thedisc pack 142. To effect the placement, the station control computer 224signals a Z-axis air slide to place an end effector 300 in matingcontact with the clampring 110. Upon engagement with the clampring 110,the Z-axis air slide 296 continues in the downward stroke causing thecomponent retainer 338 of the end effector 300 to retreat away from theclampring 110 to expose the balance correction member 158 to the annularbalance correction containment cavity 160. As the component retainer 338passes by the balance correction member 158, the balance correctionmember 158 expands slightly and enters the annular balance correctioncontainment cavity 160, the expansion continues until the balancecorrection member 158 comes to rest at the base of the annular balancecorrection containment cavity 160. The balance correction member 158 isconstrained by the annular balance correction containment cavity 160 andcontinues to exert a spring force on the annular balance correctioncontainment cavity 160 to maintain the position of the balancecorrection member 158 over the life of the disc drive 100 of FIG. 1.

Accordingly, the present invention is directed to an apparatus andmethod for balancing a rotary object, such as a disc drive disc pack. Asexemplified by preferred embodiments, a clampring 110 is used to providea clamping force to clamp discs 108 to a spindle motor hub 106 rotatableabout an axis. An annular recess (balance correction containment cavity160) is formed in the clampring which circumferentially extends aboutthe axis. A balance correction member 158 is provided as a c-shaped ringwith a substantially elliptical shape formed from a wire having aselected length and a nominally uniform cross-sectional area along theselected length. The balance correction member is compressed to asubstantially circular shape and then placed within the annular recessso that the compressed balance correction member expands andcompressingly engages the rotatable body.

In a preferred embodiment, the balance correction member is installedusing an automated balance correction station 200 having a frame 202which supports a lift and balance measure assembly 206, a lift andlocate assembly 208 and a balance correct assembly 212. The lift andbalance measure assembly measures the rotational imbalance of the discpack. The lift and locate assembly positions the disc pack for receiptof the balance correction member. The balance correct assembly releasesa balance correction member in response to the measured rotationalimbalance, compresses the balance correction member to a substantiallycircular shape, and places the compressed balance correction memberadjacent the disc pack so that the compressed balance correction memberexpands and compressingly engages the annular recess in the disc pack.

For purposes of the appended claims, it will be readily understoodconsistent with the foregoing discussion that the “nominally uniformcross-sectional area” of the claimed “balance correction member” will bedefined as a nominally uniform cross-sectional diameter of the wireacross the length of the wire, as shown by the two cross-sectional areasof the balance correction member 158 of FIG. 3, and will not be extendedto refer either to a diameter of the c-shape itself or to across-sectional area taken along another axis (such as the length) ofthe wire.

It will be clear that the present invention is well adapted to attainthe ends and advantages mentioned as well as those inherent therein.While presently preferred embodiments of the invention have beendescribed for purposes of the disclosure, it will be understood thatnumerous changes can be made which will readily suggest themselves tothose skilled in the art. Such changes are encompassed within the spiritof the invention disclosed and as defined in the appended claims.

What is claimed is:
 1. An automated balance correction stationconfigured to install a balance correction member on a disc pack of adisc drive, the balance correction member comprising a c-shaped ringwith a substantially elliptical shape formed from a wire having aselected length and a nominally uniform cross-sectional area, thebalance correction member configured for retention in a correspondingannular recess in the disc pack, the balance correction stationcomprising: a frame; a lift and balance measure assembly supported bythe frame which measures rotational imbalance of the disc pack; a liftand locate assembly supported by the frame and configured to positionthe disc pack for receipt of the balance correction member; and abalance correct assembly supported by the frame and configured torelease a balance correction member in response to the measuredrotational imbalance, compress the balance correction member to asubstantially circular shape, and place the compressed balancecorrection member adjacent the disc pack so that the compressed balancecorrection member expands and compressingly engages the annular recessin the disc pack.
 2. The automated balance correction station of claim1, further comprising a station control computer in digitalcommunication with the conveyor, the lift and balance measure assembly,the lift and locate assembly, the feature detection assembly and thebalance correct assembly to control the installation of the balancecorrection member onto the disc pack.
 3. The automated balancecorrection station of claim 1, wherein the balance correct assemblycomprises: a plurality of component feeder assemblies supported by theframe which cooperate to dispense the balance correction member from apopulation of nominally identical balance correction members of varyinglengths; a component capture and transfer assembly supported by theframe which compressingly engages the balance correction member; and apick and place manipulator assembly supported by the frame which graspsthe compressed balance correction member from the component capture andtransfer assembly and moves the compressed balance correction member tothe disc pack.
 4. The automated balance correction station of claim 3,wherein the pick and place manipulator assembly comprises: a rotaryactuator assembly comprising: a rotatable motor; and a motion controllercoupled to the rotatable motor to control the rotation of the rotatablemotor; and a manipulator arm supported by the rotatable motor andconfigured to grasp and move the compressed balance correction member tothe disc pack.
 5. The automated balance correction station of claim 4,wherein the manipulator arm comprises an end effector receiving platesupporting an end effector assembly, wherein the end effector assemblycomprises: an angle plate; and an end effector comprising: a rotaryindexing motor having a rotatable shaft supported by the angle plate forpositioning the compressed balance correction member relative to thedisc pack; a cylindrical plunger housing attached to the rotatable shaftwhich confines the compressed balance correction member; a spring-loadedcentering shaft assembly supported by the cylindrical plunger whichlocates the disc pack relative to the compressed balance correctionmember; a plunger compression spring slidingly enclosing the cylindricalplunger housing which maintains the position of the cylindrical plungerduring movement of the compressed balance correction member from thecomponent capture and transfer assembly to the disc pack and allowingretreat of the cylindrical plunger during disposition of the compressedbalance correction member onto the disc pack; and a vacuum housingattached to the angle plate assembly and adjacent the cylindricalplunger housing for removing particulate generated by the effectorassembly during operation; and a Z-axis air slide mounted between theend effector receiving plate and the angle plate providing Z-axisposition for the end effector.
 6. The automated balance correctionstation of claim 3, wherein the component capture and transfer assemblycomprises a linear actuator having an attached ring expanding gripperassembly with a gripper base and a plurality of gripper sectionsslidingly attached to the gripper base forming a variable diameterannular balance correction containment cavity, the linear actuatorpositioning the ring expanding gripper assembly adjacent the pluralityof component feeder assemblies for receipt of the balance correctionmember.
 7. The automated balance correction station of claim 6,whereupon receipt of the balance correction member the plurality ofgripper sections compressingly engages the balance correction member. 8.The automated balance correction station of claim 1, wherein the discpack has a spindle motor hub with a timing mark denoting a selectedangular position of the spindle motor hub, and wherein the automatedbalance correction station further comprises a detection systemcomprising: a downward focusing recognition assembly with a first lightsource attached to the downward focusing recognition assembly, thedownward focusing vision system recording and reporting images of theangular position of the timing mark; and an upward focusing visionsystem having an upward focusing recognition assembly with a secondlight source attached to the upward focusing recognition assembly, theupward focusing vision system recording and reporting images of theangular position of the compressed balance correction member relative tothe angular position of the timing mark.
 9. The automated balancecorrection station of claim 8, wherein each of the respective downwardand upward focusing recognition assemblies comprises a digital videocamera which provides digital image signals of the respective timingmark of the disc pack and the compressed balance correction member.